Culture system



June 11, 1968 w. E. KELLEY ET AL 3,387,587

CULTURE SYSTEM 2 Sheets-Sheet 1 Filed March '7, 1967 INVENTORS. WILL/AME. KELLEY l llllllldl,

JESSOP SMITH BY 0%, 2724A, .4 0

ATTORNEYS.

June 11, 1968 w. E. KELLEY ET AL 3,387,587

CULTURE SYSTEM Filed March 7, 1967 2 Sheets-Sheet z PREFILTRATION ICOOLING V BIOCHEMICAL FILTRATION INVENTORS. WILLIAM E. KELLEY JESSOP.SM/TH RECIRCULATION TO TANK BY 0%,ma flmzz fJg. 5 ATTORNEYS.

United States Patent Ofice 3,387,587 CULTURE SYSTEM William E. Kelley,Euclid, and Jessop Smith, Gates Mills, ()hio, assignors to AquariumSystems, Inc, Wicklitfe, Ohio, a corporation of Ohio Continuation-impartof application Ser. No. 492,693, Oct. 4, 1965. This application Mar. 7,1967, Ser. No. 633,322

18 Claims. (Cl. 1192) ABSTRACT OF THE DISCLOSURE A culture system forthe maintenance of captive marine life including a housing and a tank inwhich such life are maintained and means for controlling the tempertureof the culture medium within the tank. The culture medium is circulatedthrough biochemical filtration means associated with the tank to reactchemically therewith to replenish the alkaline reserve and to promotethe growth of bacteria therein. Means are also provided to circulate theculture medium throughout the system and to aerate the medium as it isreintroduced into the tank to facilitate gas exchange of carbon dioxideand oxygen therewith.

This application is a continuation-in-part of our copending application,Ser. No. 492,693, filed Oct. 4, 1965, now abandoned, entitled CultureSystem.

This invention relates generally as indicated to a culture system forthe maintenance of captive marine life and more particularly relates tosuch a system in which biochemical filtration is employed to maintainthe culture medium under the conditions most appropriate for thesurvival of such animals.

The use of aquariums for the maintenance and display of various forms ofmarine life in the home, schools and commercial institutions has, ofcourse, been quite popular for a long number of years. In general, suchaquariums have been fairly successful in maintaining these animals, butcertain problems have been encountered, particularly in maintaining themore delicate forms of marine life, such as invertebrates. In thesuccessful operation of a culture system, one of the most importantfactors is the maintenance of the culture medium in good condition. Thistask has proved to be especially difiicult for inland aquariums whichexhibit marine fish and invertebrates because of the difiiculty involvedin replacing sea water when it is no longer able to support the delicatemarine life.

The available evidence indicates that depletion of the alkaline reservein a marine aquarium system is the most important limiting factor in themaintenance of fishes and invertebrates and that ammonia is the nextmost important limiting factor as ammonia is extremely toxic to theseforms of marine life, with the threshold values for acute ammoniatoxicity varying from a few parts per million to less than one part permillion. Moreover, there is considerable evidence that fish suffer illeffects such as inhibition of growth and partial asphyxiation within afew days time at concentrations well below those which are lethal. Theproblem of ammonia control is extremely ditficult as it is constantlybeing produced in the system by excretion of aquarium animals and by thebreakdown of organic substances in the culture medium during use.

In the past, marine aquariums were believed to duplicate the functionsof the sea itself, but there are important distinctions between marineaquarium systems and the sea including the following:

(1) Both the alkali reserve and pH of the culture medium decreases; (2)Nitrogen compounds appear in abundance starting Patented June 11, 1968with ammonia which must be oxidized to the nitrate form;

(3) The nitrate accumulates but may approach an equilibrium value as theresult of denitrification;

(4) Bacteria numerically increase tremendously but with a great decreaseof species;

(5 The total organic content of the water increases; and

(6) The magnesium content decreases while the potassium, calcium,phosphate and sulfate contents increase.

Because of such important distinctions, the culture system of thepresent invention does not necessarily attempt to duplicate the functionof the sea but rather attempts to provide the best possible medium forthe survival of the marine life. Pursuant to the achievement of thisobjective, one of the principal problems which is encountered is thedepletion of the alkaline reserve of the culture medium by theacidifying action of the respiration of marine life introduced into thesystem and by mineralization of non-living organic materials, which areoxidative or acid forming processes. It is a principal object of thepresent invention therefore to provide a culture system in which thealkaline reserve of the culture medium can be efficiently controlled.

Another object of the present invention is the provision of a culturesystem in which the nitrogen content thereof is effectively controlled.

It is an additional object of this invention to provide a culture systemand a process for maintaining captive marine life which is suitable formaintaining the more delicate forms of marine life satisfactorily overextended periods of time.

Yet another object of this invention is the provision of a culturesystem in which biochemical filtration is employed to control thealkaline reserve and nitrogen content of the culture medium.

Other objects, features and advantages of this invention will becomeapparent to those skilled in the art after a reading of the followingmore detailed description.

These and other objects are achieved by means of the present inventionin which a culture system and process are provided for maintainingcaptive marine life utilizing a circulation system which is designed toefficiently remove acid forming carbon dioxide and in which thecirculating Water is exposed to calcareous particles to further reducethe acidity thereof andto replenish the carbonate alkalinity of theculture medium. As will be more fully explained hereinafter, thebiochemical filtration serves not only to replenish and hence controlthe alkaline reserve of the culture medium but also to promote thegrowth of nitrifying bacteria which assist in minimizing the toxiceffects of ammonia by oxidizing it to the nitrate form.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawings setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of but afew of the various ways in which the principle of the invention may beemployed.

In said annexed drawings:

FIG. 1 is a perspective view illustrating one form of the culture systemof this invention;

FIG. 2 is a section view along the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary cut-away view illustrating in greater detail thebio-chemical filtration means of this invention;

FIGS. 4 and 5 are perspective views illustrating another embodiment ofthis invention; and

FIG. 6 is a block diagram illustrating the process of this invention.

Referring now to the drawings and particularly to FIGS. 1-3, the culturesystem 1 comprises a housing 2 which has a tank 3 positioned thereon inwhich the marine life are maintained. To facilitate movement, it ismounted on rollers 4. A door 5 is provided for access to the interior ofthe housing in which a refrigeration unit 6 is provided. Therefrigeration unit is of standard manufacture, and accordingly it willnot be described in further detail.

A culture medium 7 is provided in the tank, and, in this embodiment,prefiltration means 8, which is preferably a block of foam material suchas foamed polyurethane, is provided through which the culture medium iscirculated to remove particles of organic materials therefrom whichmight otherwise contribute their nitrogen content to the formation ofammonia in the medium. As seen most clearly in FIG. 2, the culturemedium passes from tank 3 through a series of openings 9 in the bottomthereof into a. cabinet 19 which is provided in the housing adjacent theone end thereof. The interior of the cabinet is preferably coated with asuitable plastic or paint to insure that it is waterproof and non-toxicto the marine life, and cooling coils 11 and bio-chemical filtrationmeans designated generally by the numeral 12 are positioned therein. Themedium is thus circulated so that it passes through the coils, which arepreferably of a plastic material to avoid development of a toxiccondition in the medium, whereby the temperature is regulated into thebio-chemical filtration means from which it is drawn off through pipe13, which is preferably positioned beneath the housing to facilitatemore effective removal from the filter, into pumps 14 and circulatedthrough pipe 15 back into the tank. Although not illustrated electricalimmersion heating apparatus may also be associated with the filter toincrease the temperature of the medium if necessary, although generallyfor most animals, cooling rather than heating will be required.

The bio-chemical filtration means 12 comprises particulate calcareousmaterial which is supported near the bottom of the cabinet by means ofcorrugated perforated plate 16 which is positioned on a plurality ofcross bars 17, only one of which is illustrated. The performations inplate 16 are preferably positioned in the lower surface of thecorrugation and extend transversely thereof as illustrated to avoid deadspace in the filtrant and to permit complete drainage through the plate.The filter and cooling coils also have a thermostat 18 associatedtherewith to assist in the temperature control.

After the water is drawn through the bio-chemical filter, it isrecirculated to the tank and reintroduced into the culture mediumtherein through a slidable manifold 19 which has a plurality of openings20 therein to spray and aerate the culture medium as it is reintroducedto facilitate removal of carbon dioxide by gas exchange with the medium.The manifold is thus designed to be movable vertically in a track orguide means so that the water flow may be adjusted and aeration may becontrolled by adjusting the relationship between the openings and thesurface of the culture medium or eliminated by raising the manifoldabove the surface of pipe 15. Although the aeration means illustratedhas been found to be quite effective and is thus generally the preferredform, it is within the scope of the present invention to utilize otheraeration means such as a T-shaped pipe arrangement with a plurality ofopenings therein, spraying, a stream of bubbles, an air stone, etc. Anysuch means of this type be employed, so long as it provides the desiredaeration of the medium to remove the carbon dioxide therefrom andprovides a high percentage of oxygen saturation during operation.

Referring now to FIGS. 4 and 5, another embodiment of the presentinvention is illustrated. A housing 25 is provided with tank 26 thereinin which the marine life are maintained. In this embodiment, the tank isseparated by partition 27 from a compartment in which refrigeration unit23 is positioined. The bio-chemical filter 29 is positioned adjacent thebottom of the tank 26 and is supported in such position by corrugatedperforated plate 39 which is supported on cooling coils 31. The culturemedium will thus be circuated down through the biochemical filter andperforated plate and past the cooling coils and be removed from the tankthrough pipe 32. The water will thereafter be circulated by pump 33 backinto the tank through pipe 34. As in the previous embodiment, athermostat 35 is used to assist in temperature control and means areprovided for aerating the medium as it is reintroduced into the tank.

The bio-chemical filtration means used in this invention comprises aparticulate calcareous material, such as coral gravel, crushed oystershells, naturally occurring calcareous marble chips, limestone,dolomite, doloinitic limestone, etc. Especially good results have beenobtained in the maintenance of various forms of marine life when thecalcareous material is rich in magnesium, such as coral gravel or theother materials listed above in which there is sufficient magnesiumcontent to increase the water solubility of the calcareous material atthe pH and temperature set forth herein. In general such magnesiumcontent, as for example, magnesium carbonate, should be at leastapproximately four percent by weight, although this may vary dependingupon the particular material in question.

The particles size of the calcareous material may be varied dependingupon the flow rate of the culture medium through the filter and thetotal effective surface area of the filter which is required to controlthe alkaline reserve of the medium, but it is preferred for mostenvironments that the particle size be a minimum of approximately 2 mm.and normally within the range of from about 2 mm. to about 5 mm.Calcareous material such as coral gravel is preferred because it isextremely porous in nature and hence provides an effective surface areafor the desired biological and chemical reactions which is far greaterthan expected in view of the particle size of the material.

During normal operation of the aquarium as the culture medium iscirculated, the calcareous material will undergo a chemical reactionwith the medium thereby producing bicarbonate ions and thus serving as abuffering agent and increasing the alkalinity of the medium. It is inthis manner that the calcareous material acts as a chemical filter andcontrols the alkaline reserve of the culture medium.

Due to the porosity and surface area of the calcareous material, it willalso function as a biological filter in the system to provide attachmentsites for bacteria to grow which will nitrify the nitrogen appearing inthe culture medium in the form of ammonia to the nitrate form in whichit is relatively harmless to the marine life. For the successfulmaintenance of such life, it is essential that the nitrogen whichinitially appears as ammonia be oxidized to the nitrite and then to thenitrate form by the bacteria in a relatively short period of time, andhence a large effective surface area must be provided for the bacteriato grow upon and this surface area must be brought into contact with allof the water in the culture system. For satisfactory maintenance of themore delicate forms of marine life, a nitrogen content in the culturemedium in the form of nitrates of less than 50 parts per million partsof the medium is desirable.

Another environmental factor which influences the nitrogen cycle of theculture system is the pH of the culture medium. For example, a low pHinhibits the oxidation of ammonia which is so extremely important to theachievement of satisfactory results. It has been found that satisfactoryresults are achieved when the pH of the culture medium is maintained ata minimum of approximately 8.0, with a pH of about 8.2 being preferred.Similarly, the temperature of the culture medium is important, sincemost marine organisms do not live well outside of their normal range innature. For practical operations,

the temperature should be maintained within the range of approximately35 to 80 F. This upper temperature is approximately the ambientoperating temperature in most installations and thus temperature controlis usually a matter of cooling.

In the process of the present invention, the culture medium iscirculated throughout the system in such a manner as to permit themedium to be in contact with the calcareous filtrant for a timesuflicient to control the alkalinity of the medium and to promote thegrowth of the nitrifying bacteria. This flow rate will vary dependingupon the size and effective surface area of the biochemical filter, butin general it has been found that the turnover rate of the mediumthrough the filter should be a minimum of about 4 times per hour.Similarly, for best results, the flow rate of the medium through thecalcareous filtrant should be approximately 2 gallons per square foot ofsurface area of a horizontal section of the filtrant per minute. Theratio of the filtrant volume to the weight of the animals beingmaintained should also preferably be at least about 1 cubic foot perpound of animal Weight, and the ratio of the volume of culture medium tothe living animal weight should preferably be approximately 100 gallonsto about 2 pounds for the more delicate animals, although a greaterweight of animals can be tolerated for the less delicate animals.

A particularly suitable culture medium for use in this invention is thatdisclosed in the co-pending application of Kelley and Segedi, Ser. No.423,604, entitled Synthetic Sea Water Composition.

The bio chemical filtration means used in this invention will normallyconsist entirely of the described calcareous material, but may, ifdesired, include certain other materials such as charcoal which would beused as an adsorbent in the filter.

If a large quantity of marine life is being maintained, theprefiltration means illustrated in the embodiment of FIGS. 1-3 ispreferably used which serves as a physical filter or strainer in thesystem to remove the pieces of organic material in the culture mediumwhich would otherwise contribute their nitrogen content to the formationof ammonia. In the form illustrated, the filter is simply a foam block,but other similar means may be used to achieve this purpose. Similarly,a diatomaceous earth filter, such as any of the standard commerciallyavailable accessory units, may be used periodically to remove suchorganic particles and clarify the water.

For special culture problems, other modifications may be made to thesystem, such as the employment of sidehung trays in the tank toaccommodate many small compartments to isolate organisms under culture.Also, a mud, clay, sand, gravel, etc, substrate may be constructed overa fine nylon cloth placed on a perforated substrate plate positioned inthe main body of the tank for the culture of bottom dwelling organisms.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims, or the equivalent ofsuch, be employed.

We therefore particularly point out and distinctly claim as ourinvention:

1. A culture system for the maintenance of captive marine liftcomprising a housing, a tank positioned on said housing in which suchmarine life are maintained, means associated with said tank forcontrolling the temperature of a culture medium therein, bio-chemicalfiltration means comprising particulate magnesium rich calcareousmaterial associated with said tank through which such culture medium iscirculated to react chemically with such culture medium to replenish thealkaline reserve thereof and to maintain the pH of such medium at aminimum of approximately 8.0, said particulate material being ofsufficient particle size and total surface area to provide attachmentsites to promote the growth of nitrifying bacteria therein, and means tocirculate such medium through said filter and to reintroduce such mediumto said tank, said circulation means including means to aerate suchmedium upon reintroduction into said tank of facilitate gas exchange ofcarbon dioxide and oxygen with such medium.

2. The system of claim .1 in which said bio-chemical filtration means ispositioned in the bottom of said tank.

3. The system of claim 2 including a perforated plate positioned nearthe bottom of said tank on which the calcareous material is positioned.

4. The system of claim 1 in which said particulate calcareous materialis at least approximately 2 mm. in particulate size.

5. The culture system of claim 1 in which said particulate material isselected from the group consisting of coral gravel, crushed oystershells, naturally occurring calcareous marble chips, limestone, dolomiteand dolomitic limestone.

6. The culture system of claim 5 in which the magnesium content of saidparticulate material is at least approximately 4% by Weight.

7. A culture system for the maintenance of captive marine lifecomprising a housing, a tank on said housing in which such marine lifeare maintained, means associated with said tank for controlling thetemperature of the culture medium therein, a cabinet beneath said tankadjacent one end thereof, bio-chemical filtration means comprisingparticulate magnesium rich calcareous material positioned in saidcabinet, means to circulate such culture medium through saidbio-chemical filtration means and to reintroduce such medium to suchtank, whereby the alkaline reserve of such culture medium is replenishedby chemical reaction between such medium and said calcareous materialand the pH of such culture medium is maintained at a minimum ofapproximately 8.0, said particulate material being of sufficientparticulate size and total surface area to provide attachment sites topromote the growth of nitrifying bacteria therein, said-circulationmeans including means to aerate such medium upon reintroduction intosaid tank to facilitate gas exchange of carbon dioxide and oxygen withsuch medium.

8. The system of claim 7 including prefiltration means in said tankwhereby such medium is circulated therethrough prior to circulationthrough said bio-chemical filtration means.

9. A process for maintaining captive marine life comprising circulatinga culture medium through the area where such marine life are maintained,circulating such medium through a bio-chemical filtration means ofparticulate magnesium rich calcareous material to react chemically withsuch material to replenish the alkaline reserve thereof at a ratesufficient to maintain the pH of such medium at a minimum ofapproximately 8.0, said particulate material being of sufficientparticle size and total surface area to provide attachment sites topromote thegrowth of nitrifying bacteria in such medium, circulatingsuch medium to such area where such marine life are maintained, andaerating such medium at the place of introduction into such area tofacilitate gas exchange of carbon dioxide and oxygen with such medium.

10. The process of claim 9 in which the flow rate of the culture mediumthrough the bio-chemical filtration means is approrimately 2 gallons persquare foot of surface area of a horizontal section of the filtrationmeans per minute.

11. The process of claim 9 in which the turnover rate of culture mediumthrough the filtration means is a minimum of 4 times ,per hour.

12. The process of claim 9 in which the ratio of the filtrant volume tothe animal weight thus maintained is at least approximately 1 cubic footto one pound of animal weight.

13. The process of claim 9 in which said particulate material isselected from the group consisting of coral gravel, crushed oystershells, naturally occurring calcared 0115 marble chips, limestone,dolomite and dolomitic limestone.

14. The process of claim 13 in Which the magnesium content of saidparticulate material is at least approximately 4% by Weight.

15. The culture system of claim 7 including a perforated corrugatedplate positioned near the bottom of such tank on which said particulatecalcareous material is positioned.

16. The culture system of claim 15 in which said perforations in saidcorrugated plate are in the lower surface of said plate to avoid deadspace in said filtration means and to permit complete drainage throughsaid plate.

17. The culture system of claim 16 in which said perfon 0 rations extendtransversely of the corrugations in said plate.

18. The process of claim 9 in which the pH of the culture medium ismaintained within the range of approximately 8.0 to approximately 8.2.

References Cited UNITED STATES PATENTS 2,594,474 4/1952 McGrath 119-52,672,845 3/ 1954 Schneithorst 119--5 3,025,831 3/1962 Berardi 119-23,146,195 8/ 1964 Berardi l19--5 X HUGH R. CHAMBLEE, Primary Examiner.

